The spinal columns of humans or animals are constructed from a plurality of vertebrae arranged one above another. They are interconnected both in a load-bearing manner and also in an articulated manner. For this purpose, the vertebrae have a structure with a solid vertebral body with two osseous projections (pedicles) which protrude laterally and to the rear and which, in their rear region, are connected by an osseous arch. In the connection area, the osseous arch is broadened (lamina) and has, at its center, a rearwardly protruding spinous process. The spinous process and two further transverse processes on the side surfaces of the pedicles form articulation points for muscles and ligaments. In the area where the pedicles merge into the lamina, an upper and a lower articulating process are arranged on each side. These each form part of a facet joint with an adjacent upper or lower vertebra. For load-bearing connection to the adjacent upper and lower vertebra, intervertebral disks are in each case provided which are arranged at the bottom and/or top on relatively flat cover surfaces of the vertebral body. The space bounded by the rear side of the vertebral body and by the vertebral arch forms a hollow space (spinal canal) in which nerve fibers running parallel to the spinal column are accommodated. It has been found that pressure is exerted on the nerve fibers when they become pinched or trapped, particularly on account of osseous growth in the area of the spinal canal or on account of protrusions of the intervertebral disk (so-called herniated disk), and that this may cause severe back pain.
For therapy, it is known to at least partially open the vertebral arch in order to create an access route to the spinal canal. There, the growths causing the problems are removed by means of instruments known per se, and the pressure is thus removed from the nerve fibers. The pain induced by the pressure is in this way correspondingly reduced. In this method, also known as laminectomy or decompression, the access created in the lamina, that is to say the opening present therein, is in most cases not closed after the operation. It has been shown that this weakens the mechanical stability of the vertebra.
It has been proposed by the applicant, in an earlier patent application, to make available an implant set comprising reinforcement implants in various sizes. They have a rhombus-shaped filler body which is inserted into and fills the opening created by the laminectomy. The rhombus-shaped filler body bears with its two opposite side surfaces on the resection surfaces of the lamina. In this way, the laminar arch is again made complete by the insertion of the filler body, such that it can again bear loads and, in particular, does not collapse under compressive loads. To be able to fill the resected area as completely as possible and without expanding it, the reinforcement implant has to be provided in a considerable number of different sizes (at least seven) per side (left or right). This means considerable complexity of the implant set. Moreover, for the desired function of transfer of pressure, it is important that the lateral faces of the filler body lie as flat as possible on the resection surfaces of the lamina. Since the resection surfaces are often not quite plane in practice, the transfer of pressure is impaired. Another consideration is that the insertion of the filler body is made difficult when the resection surfaces are not plane, and this causes additional complications.